Google's Cloud

Google Sites

is a SaaS offering a simple web page editor plus 10 GB free family web space →
Google sites.
Google Sites competes with Microsoft Office Live Workspace.
Drawback: There is no way to write or import html-code directly.

Google Docs

is a SaaS offering a simple text editor plus a good spreadsheet program together with generous free web space. All documents can be shared with other Google Docs users but it is unclear what comes out when 2 persons edit the same document at the same time . When you view the HTML-source codes you will detect that both the text editor and the spreadsheet program convert your input into an incredibly big and complicated html-file.
There is a good "Print Preview" that converts everything into a raster image.
Drawback: You cannot upload other file types than GoogleDoc.See:
Google Documents,
Wikipedia: Google Docs,
Welcome to Google Docs

Google AppEngine

is the name of Google's cloud PaaS to write and run user web applications. There is a Python and a Java development kit: App Engine SDK.
For debugging and testing, AppEngine is able to simulate the server on the developer's local computer.After writing and local testing you can upload and run your web application under the free (up to 10 apps, 500 MB altogether) www.appspot.com domain.
See: What Is Google App Engine?

GoogleWave

is a platform that mixes shared GoogleDocs with a the messenger service GoogleTalk together with a developer API.GoogleWave (still in Beta stage) is a mixture of conversation, translation and shared document services.
Developers can extend and embed the GoogleWave services into their own web applications.

GDrive

Google seems to work on an exciting project: "GDrive provides reliable storage for all of your files, including photos, music and documents. ... GDrive allows you to access your files from anywhere, anytime, and from any device -- be it from your desktop, Web browser, or cellular phone."
See: InformationWeek: Where's Google GDrive?